1. Field of the Invention
The present invention relates to a Ni-base alloy, a heat-resistant spring made of the alloy and a process for producing the spring, and more particularly to a Ni-base alloy which has high resistance to permanent set at high temperature, can be produced at low cost, and thus is suited especially as a material for heat-resistant springs.
2. Description of the Related Art
Heat-resistant springs are used in an exhaust gas system for an automobile engine, an airplane engine and the like. Such heat-resistant springs need to be made of a material having high-temperature strength and high resistance to permanent set.
As the material of such heat-resistant springs, heat-resistant alloys such as A286™, Inconel® X750, Inconel® 718 and Refractaloy™ are exemplified in “Data Collection for high-temperature strength of heat-resistant spring and materials therefor” (1986) published by Spring Technology Association, and “Data of high-temperature strength for heat-resistant spring and materials therefor (continued)” (1989) published by Spring Technology Association.
In these days, heat-resistant springs are required to have even higher resistance to permanent set at elevated temperatures than convention springs and at the same time be produced at low cost.